Field of the Invention
The present invention relates to a pacer connector assembly for connecting a cardiac pacing lead to a pacer, and more particularly to a pacer connector assembly which readily connects with the proximal end of an in-line multielectrode pacing lead. The connector assembly is designed to be expandable to accommodate and connect with a plurality of connector bands on the proximal end portion of the pacing lead and includes a soft, pliable, so-called pacer neck which has a socket for receiving the proximal end of the pacing lead. The assembly further includes spaced apart conductive elastomeric connectors in the neck and a removable wedge for squeezing the connectors against the connector bands on the pacing lead.
Description of the Prior Art
A pacing system includes a pacer, which comprises a metal container or case that contains electronic circuitry and a power supply, and a pacing lead. The proximal end of the lead is connected to output terminals of the pacer in a component of the pacer which is commonly referred to as the neck of the pacer mounted to a top side of the case.
Multiple eletrode cardiac pacing leads are well known and have been utilized for pacing both the atrial and ventricular chambers of the heart. Such a pacing lead includes a multipolar electrode assembly at the distal end and terminal connector bands or rings at the proximal end. The multipolar electrodes at the distal end of the lead usually comprise a tip electrode and one or more ring electrodes along the length of the lead. Additionally, the lead may contain one or more sensors along its length which measure and monitor physiological parameters such as, for example, ejection time, pressure of blood in a ventricle or the partial pressure of oxygen or carbon dioxide within the chambers of the heart.
In a pacing system with one electrode on the pacing lead, the distal end or tip of the lead contains the electrode and is usually placed in the ventricle of the heart. The electrode is connected to the lead by an insulated helically coiled wire conductor. At the proximal end of the lead, a terminal pin is affixed to the lead. This pin is inserted into a socket in the pacer neck where it makes contact with an electrical connector socket which is, in turn, connected to cardiac pacer electronic circuitry and a power source in the pacer case.
With one electrode on the distal end of the lead, the pacer system is referred to as a unipolar system. Then one pacer lead connector is needed in the neck of the pacer to serve as a cathode connector, with the case or can of the pacer, which is normally metal, serving as an anode. In a bipolar system, where two electrodes are on the distal end of the lead, a pacing lead terminal pin and terminal connector band are provided on the proximal end of the lead and two pacer lead connectors are necesssary in the neck of the pacer.
Currently, cardiac pacing sytstems focus upon (a) the sensing of electrical signals generated by the myocardium or middle layer of the atrial and/or ventricular chambers of the heart and (b) the stimulation of one or both of these chambers in the absence of spontaneous electrical activity. In such a dual chamber system, either two different leads are used or the lead used measures ventricular activity at its tip and atrial activity along its length and therefore, more than one connector is needed in the pacer neck. In dual chamber unipolar systems, two pacer lead connectors are required in the neck of the pacer, one for the atrial lead terminal connector pin or band and one for the ventricular lead terminal connector pin or band. In a bipolar dual chamber system, four pacer lead connectors are required in the pacer neck for connecting to pacing lead proximal terminal connectors, such as a terminal pin and three connector bands for monitoring both chambers of the heart.
Future pacing systems will include physiological sensors, either as part of the pacing lead or separate from it. These physiological sensors will measure parameters such as oxygen or carbon dioxide levels in the blood, ventricular blood pressure, ejection time, pH, or any combination thereof, to name a few. These parameters will be transmitted to the pacer circuitry for use in setting various pacer outputs. Additionally, each of these sensors will require an electrical contact or connector within the pacer neck in addition to the contacts or connectors described above for connection to the electrodes for sensing electrical activity.
Multielectrode pacing leads most suitable for this type of electrode and sensor system include a lead with multiple ring electrodes and sensors on the distal end and multiple spaced apart connector bands on the proximal end of the lead in an in-line arrangement and isodiametric with the lead. Such a lead allows the monitoring of several different parameters while only causing one insertion to be made into the heart which reduces trauma. An example of such a lead is disclosed in U.S. Pat. No. 4,469,104 which discloses a lead assembly for a body implantable tissue stimulator which contains a connector system of a terminal electrode assembly on the proximal end of the lead and a connector assemby in the pacer neck which relies on garter springs or conductive elastic O-rings to contact each, in-line spaced apart connector band or ring on the proximal end of the lead. Although such a lead is effective, the connectors used are hard to manufacture, are difficult to insert into the pacer neck and are too large to accommodate a large number of connector bands within the minute confines of the pacer neck.
Heretofore various connectors have been utilized for connecting the proximal end of a single or multielectrode pacing lead to the electrical outputs in the neck of a pacer. The most common type of connector system employs a terminal pin on the proximal end of the pacing lead which is secured inside the neck to a connector of the pacer by a set screw. This arrangement is not completely desirable since it usually requires the surgeon to tighten the screw after the terminal pin of the lead is in place inside the neck of the pacer during implantation in a body. Such a procedure is complicated due to the small size of the screw and the conditions of the operating room.
Additionally, the number of terminal connector bands or rings on multielectrode lead is restricted if a different set screw is needed in the connector assembly for each terminal connector band or ring on the pacing lead. Present connector assemblies which employ set screws are limited to a maximum of four set screw connectors for four pacing lead terminal connectors, e.g., a pin and three bands, due to the size limitations of the pacer neck.
Finally, the set screws encounter problems with body fluids over an extended period of time which cause deterioration of a screw and entry of fluid into the electrical contact area causing damage and malfunction. In some pacer systems, a cap has been used to cover the screw head but such a system has not been entirely effective and has further complicated the pacer installation procedure.
Therefore, the need exists for a multiple contact connector assembly in a pacer neck which is small in size, easy to manufacture, readily accommodates a multielectrode lead, is impervious to body fluids and can be adapted to receive and make contact with a number of connector bands or rings on the lead, the number being variable and dependent upon the number of distal electrodes and sensors required for a particular patient.
As will be described in greater detail hereinafter, the assembly of the present invention provides a device which is capable of readily accommodating the proximal end portion of an in-line multielectrode lead without any additional complex installation procedures and is completely sealed from the body it is implanted in.
Moreover, the connector assemby of the present invention differs from previously proposed connector assemblies and pacer neck constructions by providing a connector assembly and pacer neck construction which is small in size, contains its own lead strain relief, is easy to use, can accommodate a large number of terminal connector bands, provides removable means for placing pressure against the contacts or connectors engaging the connector bands on a pacing lead, is easy to manufacture, and which maintains high reliability of electrical contact between each assembly connector/connector band connection throughout the life of the pacing system.